This invention relates to electrical interconnection apparatus and particularly to such apparatus for establishing connections between integrated circuit boards and the like and flat, flexible electrical cables which are microstrip transmission lines.
The introduction of miniaturized integrated circuits in present-day communications and electronics systems has contributed significantly to system cost reduction, reliability, and, importantly, to overall size reduction. These circuits are formed by fabricating many individual electrical components and their interconnections simultaneously on a single silicon chip, as is known. Individually packaged integrated circuits are then mounted on printed wiring boards which then become the basic system circuit modules. Since the integrated circuit interconnections are also miniaturized and, therefore, greatly reduced in length, higher system operating speeds are also achievable. The extent to which the extremely short signal paths within an integrated circuit may be taken advantage of, however, is limited by the signal path lengths and inductance interconnecting the integrated circuit boards and other system elements. In some known system arrangements, individual circuit boards are interconnected by a common flat electrical cable, the conductors of which make contact with particular circuit board terminals. Interconnection apparatus for making the connections between board and cable have in the past thus been designed to maintain to a minimum the length of the electrical paths between the two and this also comprises one of the problems to which the interconnection apparatus of the present invention is directed.
In addition to the requirement of presenting minimum signal path length, interconnection apparatus of the character here contemplated must also ensure positive and reliable electrical connections and be relatively uncomplicated in order to maintain fabrication and operating costs also to a minimum. Finally, the interconnection apparatus must permit the ready insertion of an integrated circuit board and the alignment of its terminals with the cable conductors without the risk of damage or deformation of the board terminals. The latter goal, as is known, is generally achieved when the board insertion force is zero or near zero. Known prior art interconnection apparatus for electrically connecting integrated circuit boards and flat cables fall short in more or lesser degree in meeting the aforementioned and other criteria. One such arrangement disclosed in U.S. Pat. No. 4,054,348 of J. R. Stroupe et al., issued Oct. 18, 1977, for example, requires that apertures be provided in the circuit boards for admitting elements of the connecting apparatus. U.S. Pat. No. 4,023,877 of W. M. Hennessey et al., issued May 17, 1977, discloses connector apparatus in which the cable conductors are threaded through slots provided therefor, the conductors then being urged against the circuit board terminals by a flexible member of a material such as Neoprene, for example.